Widespread vegetative compatibility groups in the dry-rot fungus Serpula lacrymans.

Serpula lacrymans is the most notorious decayer of wooden buildings in temperate regions. The occurrence of geographically widespread vegetative compatibility groups (VCG) in S. lacrymans in Europe is demonstrated in this study. Among 22 heterokaryotic isolates of S. lacrymans, five VCG were found. The most widespread VCG included isolates from Belgium, south and central Norway, separated by more than 1500 km. No other genetic variation, measured as DNA sequence variation or ISSR polymorphisms, was detected between the investigated S. lacrymans isolates, whereas a considerable level of genetic variation was found among five European isolates of the sister taxon, S. himantioides. It is hypothesised that isolates of S. lacrymans have lost their ability to recognize self from nonself due to sharing of similar VC alleles, caused by a recent genetic bottleneck during the establishment in northern Europe. Isolates re-isolated from overlapping mycelial zones between different compatible isolates had significantly slower growth than that of the original isolates and the different isolates within a VCG had different growth morphology, indicating that isolates within a single VCG may belong to different genets.